1. Field of the Invention
The present invention generally relates to an apparatus and method for allowing a single central site modem with a low processing power digital signal processor (DSP) to handle numerous digital subscriber lines (DSL). The modem apparatus and method takes advantage of the bursty nature of Internet data traffic to allow the low processing power DSP-equipped modem to handle multiple lines simultaneously.
2. Background of Related Art
As known in the art, some modems can utilize a single processor to control multiple lines. However, these modems require that the single DSP processor be fast and powerful enough to support all the multiple lines at one time. An example of this configuration is described in the commonly assigned U.S. Pat. No. 4,637,035 (hereby incorporated by reference), which shows a single processor that can control multiple lines. However, this patent requires that the single-DSP processor have enough processing power to support all the multiple lines that are attached because each line requires that the modulation be constantly active.
Heretofore, modems have lacked the ability to couple multiple local loops to a single DSP, wherein this DSP has less processing power than that needed to handle all the local loops simultaneously. This DSP can take advantage of the "bursty" nature of Internet data traffic to allow every user to achieve full throughput.
Also, as known in the art, some modems can utilize "modem pooling" and "oversubscription" to allow a smaller number of modems to handle a larger number of local loops. An example of this technology is described in the commonly assigned U.S. Pat. No. 5,668,857, which shows a plurality of modems handling a larger plurality of local loops and which is incorporated herein by reference. Modem pooling is premised upon the philosophy that not all users desire to be connected at the same time. However, once connected, the modems will always modulate a signal on the line--whether data is being transferred or not. These modem pools cannot take advantage of the "bursty" nature of Internet data traffic. Modem pools also suffer from the problem that a user will receive a "busy" indication--and not receive a connection--if the number of users attempting to connect at the same time exceeds the "oversubscription" ratio.
Modem pools also make use of complete modems--each modem having a complete analog front end and bit pump processor. Complicated analog switching is used to switch the local loops to the appropriate modem. This type of switching is subject to noise floor problems. These modem pools cannot use a plurality of local loops that are connected to a single DSP via robust digital switching.